rangechain

Chain together lazily computed modifications to range-able containers. E.g. slices, arrays, maps, and channels.

Install

Require github.com/halprin/rangechain in your go.mod file or use go to add it.

$ go get github.com/halprin/rangechain

API

Start by importing the package.

import "github.com/halprin/rangechain"

Start the Chain

To start the chain, use the From* functions. They take a range-able container, and you'll pick the appropriate one for the type of container.

container := []int{987, 3, 26}
chain := rangechain.FromSlice(container)

Function	Arguments	Description
FromSlice	• slice - A slice to be used to start the chain.	Starts the chain with the supplied slice. Chaining and terminating methods can now be called on the result.
FromArray	• array - An array to be used to start the chain.	Starts the chain with the supplied array. Chaining and terminating methods can now be called on the result.
FromChannel	• channel - A channel to be used to start the chain.	Starts the chain with the supplied channel. Chaining and terminating methods can now be called on the result.
FromMap	• aMap - A map to be used to start the chain.	Starts the chain with the supplied map. Chaining and terminating methods can now be called on the result. The singular value used to represent the key and value pairs is keyvalue.KeyValuer of github.com/halprin/rangechain/keyvalue.

From there, one can call a plethora of additional methods to modify the container passed in originally. The methods are outlined below. The methods fall into one of two categories: chaining or terminating.

Value Types

Because Go does not support generics (yet), this library operates using interface{}. One using this library may need to use type assertions.

For example, something like actualValue := value.(int).

For another example...

stringSlice := []string{"DogCows", "goes", "Moof", "Do", "you", "like", "Clarus", "the", "DogCow"}
chain := FromSlice(stringSlice)

outputSlice, _ := chain.
    Map(func(value interface{}) (interface{}, error) {
        stringValue := value.(string)
        return stringValue + " not", nil
    }).Slice()

Notice stringValue := value.(string) above. This allows one to do the string concatenation on the next line because the + operator doesn't work on an interface{} type.

Continuing the Chain

Chaining methods apply some modification to the values in the container values, but keeps the chain alive. This allows additional chaining methods to be subsequently called on the result. The subsequent chain methods operate on any changes performed by the previous chain method. Because modifications are lazily computed, none of the modifications from chaining methods are applied until after a terminating method is called.

Method	Description
Map	Will run the mapFunction parameter function parameter against all the values in the chain. In that function, return what you want to change the value into or an optional error if an error is encountered.
MapParallel	Will run the mapFunction parameter function against all the values in the chain in parallel. In that function, return what you want to change the value into or an optional error if an error is encountered. There is overhead to running in parallel so benchmark to ensure you benefit from this version.
Filter	Will run the filterFunction parameter function against all the values in the chain. In that function, on return of true, the value will stay, or on false, the value will be removed.
FilterParallel	Will run the filterFunction parameter function against all the values in the chain in parallel. In that function, on return of true, the value will stay in the chain, or on false, the value will be removed from the chain. There is overhead to running in parallel so benchmark to ensure you benefit from this version.
Skip	Skips over the parameter skipNumber number of values and effectively removes them from the chain. Also skips over any errors previously generated.
Limit	Stops the chain after the parameter keepSize number of values. Any elements afterward are effectively removed.
Distinct	Removes any duplicates.
Flatten	Will iterate over all the values in the chain, but any value encountered that is a range-able container itself will also have its values iterated over first before continuing with the remaining values in the chain. Maps flatten to its keyvalue.KeyValuer key and value pairs.
Sort	Sorts the chain given the Less function returned from the returnLessFunction function parameter. The returnLessFunction function is called with the entire serialized chain as a slice and returns a function that satisfies the same requirements as the Interface type's Less function. See the TestSortingMaps example. This method is expensive because it must serialize all the values into a slice first.
Reverse	Reverses the order of the chain. The last item will be first, and the first item will be last. This method is expensive because it must serialize all the values into a slice first.

Terminating the Chain

Terminating methods also apply some modification, requests some information, or executes something on the values. They stop the chaining by returning an actual value. This value will depend on all the previous chaining methods being executed first.

Method	Description
Slice	Serializes the chain into a slice and returns it. Also returns an error if any previous chain method generated an error. If an error is returned, the slice is filled in until the error was encountered.
Channel	Serializes the chain into a channel. Also returns any errors in a channel if any previous chain method generated an error. If an error is returned, the value channel is closed, the error is sent on the error channel, and the error channel is closed.
ForEach	Will run the forEachFunction parameter function across all the values in the chain. Also returns an error if any previous chain method generated an error. If an error is encountered, the function stops executing against the remaining chain.
ForEachParallel	Will run the forEachFunction parameter function across all the values in the chain in parallel. Also returns an error if any previous chain method generated an error. If an error is encountered, the function stops executing against the remaining chain. There is overhead to running in parallel so benchmark to ensure you benefit from this version.
Count	Returns the number of values in the chain. Also returns an error if any previous chain method generated an error. Count returns an accurate number even if an error is encountered.
First	Returns just a pointer to the first value in the chain. If the chain is empty, returns nil. Also returns an error if any previous chain method generated an error that affects the first value.
Last	Returns just a pointer to the last value in the chain. If the chain is empty, returns nil. Also returns an error if any previous chain method generated an error that affects the last value.
AllMatch	Will run the allMatchFunction parameter function across all the values in the chain. If every allMatchFunction function invocation returns true, this method returns true. If a single allMatchFunction function invocation returns false, this method returns false. Also returns false and an error if any previous chain method generated an error or if an error is returned from the allMatchFunction function.
AnyMatch	Will run the anyMatchFunction parameter function across all the values in the chain. If any anyMatchFunction function invocation returns true, this method returns true. If every invocation anyMatchFunction invocation returns false, this method returns false. Also returns false and an error if any previous chain method generated an error or if an error is returned from the anyMatchFunction function.
NoneMatch	Will do the exact opposite of AnyMatch when it comes to the boolean return value. Returns an error for the same reasons as AnyMatch.
Reduce	Applies the reduceFunction parameter function to two values in the chain cumulatively. Subsequent calls to reduceFunction uses the previous return value from reduceFunction as the first argument and the next value in the chain as the second argument. A pointer to the final value is returned. If the chain is empty, nil is returned. Also returns an error if any previous chain method generated an error or if an error is returned from the reduceFunction function.
ReduceWithInitialValue	Applies the reduceFunction parameter function to two values in the chain cumulatively. Subsequent calls to reduceFunction uses the previous return value from reduceFunction as the first argument and the next value in the chain as the second argument. The parameter initialValue is placed before the entire chain and therefore is the first argument on the first invocation of initialValue. The final value is returned. If the chain is empty, initialValue is returned. Also returns an error if any previous chain method generated an error or if an error is returned from the reduceFunction function.

Examples

See example_test.go file for some examples.